Please cite as: Mazdab, F.K. (2009) Characterization of flux-grown trace-element-doped titanite using the high-mass-resolution ion microprobe (SHRIMP-RG). The Canadian Mineralogist 47, pp. 813-831.
Abstract: Crystals of titanite can be readily grown under ambient pressure from a mixture of CaO, TiO2 and SiO2 in the presence of molten sodium tetraborate. The crystals produced are euhedral and prismatic, lustrous and transparent, and up to 5 mm in length. Titanite obtained by this method contains approximately 4300 ppm Na and 220 ppm B contributed from the flux. In addition to dopant-free material, titanite containing trace alkali and alkaline earth metals (K, Sr, Ba), transition metals (Sc, Cr, Ni, Y, Zr, Nb, Hf and Ta), rare earth elements (REE), actinides (Th, U) and p-block elements (F, S, Cl, Ge, Sn and Pb) have been prepared using the same procedure. Back-scattered electron (BSE) imaging accompanied by ion microprobe (SHRIMP-RG) analysis confirms significant incorporation of selected trace elements at lattice sites. Regardless of some zonation, the large crystal size and broad regions of chemical homogeneity make these crystals useful as experimental starting material, and as matrix-matched trace element standards for a variety of microbeam analytical techniques where amorphous titanite glass, heterogeneous natural titanite or a non-titanite standard may be less than satisfactory. Trace-element-doped synthetic crystals can also provide a convenient proxy for a better understanding of trace element incorporation in natural titanite. Comparisons with igneous, authigenic and high-temperature metasomatic titanite are examined. Extreme high mass resolution SIMS also demonstrates the analytical challenges inherent to any in-situ mass spectrometry-based analysis of titanite, due to the production of difficult-to-resolve molecular interferences. These interferences are dominated by Ca-Ca, Ca-Ti and Ti-Ti dimers that are significant in the mass range of 80-100, affecting all isotopes of Sr and Zr, as well as 89Y and 93Nb. Methods for the evaluation of these dimer interferences, and of polyatomic interferences on the LREE are discussed.
***Erratum***: The preferred value for [Pb] in the BLR-1 titanite standard is incorrectly listed in Table 3 as 19.7 ppm; the actual total [Pb] should be ~60 ppm. Although the isotopic breakdown is not specified, it should be approximately 0.04 ppm [204Pb], 46 ppm [206Pb], 4 ppm [207Pb] and 10 ppm [208Pb]. These values are consistent with an age of 1047 Ma, the present day preferred concentrations of ~300 ppm [U] and ~186 ppm [Th], and the additional contribution from minor non-radiogenic Pb. If you download this paper, please annotate these corrections in the table.
Please cite as: Mazdab, F.K. (2003) The diversity and occurrence of potassium-dominant amphiboles. The Canadian Mineralogist 41 (6) pp.1329-1344.
Abstract: Currently, the Commission on New Minerals and Mineral Names (CNMMN) of the International Mineralogical Association (IMA) recognizes seven amphibole species where potassium is the dominant A-site cation. These include potassic-ferrisadanagaite, potassic-fluororichterite, potassic-magnesiosadanagaite, potassicpargasite, potassicsadanagaite, potassic-chloropargasite and potassicleakeite. However, during the course of evaluating Cl-bearing amphibole compositions from iron-oxide-rich ore systems and comparing them with reviewed literature data, it was observed that fourteen additional naturally occurring potassium-dominant amphiboles can be justified from selected published chemical analyses using recommended normalization protocols. In keeping with accepted amphibole nomenclature, these new amphibole end-members would be “potassichastingsite”, “potassic-chlorohastingsite”, “potassic-ferropargasite”, “potassic-chloro-ferropargasite”, “potassic-aluminosadanagaite”, “potassic-chlorosadanagaite”, “potassic-chloro-ferro-edenite”, “potassicrichterite”, “potassic-ferrorichterite”, “potassic-fluoro-magnesiokatophorite”, “potassic-ferritaramite”, “potassic-magnesio-arfvedsonite”, “potassic-fluoro-magnesio-arfvedsonite” and “potassickornite”. In several of the potassium-dominant amphiboles evaluated, chlorine is an important OH-site component even when not the dominant anion, and the optional modifier “chlorian” is appropriate. Indeed, various species of both Cl-rich and K-rich ferropargasites and hastingsites (both sensu lato) are characteristic amphiboles of certain iron-oxide-rich hydrothermal systems associated with alkali-chloride metasomatism. At one locality, another new chlorine-dominant amphibole, although lower in potassium, is also observed: potassian “chlorosadanagaite”. In addition to mineralization related to hypersaline fluids, the “potassic-” amphiboles are otherwise widespread in many diverse igneous, metamorphic, and metasomatic environments. It is hence desirable and justifiable, notably for those analyses accompanied by crystallographic and physical property data, to confer species status to these amphiboles.
Please cite as: Mazdab, F.K., Johnson, D.A. and Barton, M.D. (2008) Trace element characteristics of hydrothermal titanite from iron-oxide-Cu-Au (IOCG) mineralization. Geochimica et Cosmochimica Acta 72(12) (S1) p. A609.
Abstract: Hydrothermal titanite is a common accessory mineral in the alkali-chloride alteration assemblages accompanying iron oxide-Cu-Au (IOCG) mineralization. Sensitive High Resolution Ion Microprobe-Reverse Geometry (SHRIMP-RG) trace element analyses of titanite from a suite of worldwide IOCG deposits of diverse age and host rock composition have several distinctive features that differentiate these metasomatic titanites from those of associated igneous or metamorphic origins. The most notable difference is in the relative distribution of the rare earth elements (REE). Regardless of host rock composition, the IOCG metasomatic titanite is notable enriched in the light REE, peaking at La (sometimes Ce), with values up to 20000 times chondrite in some cases. Magmatic titanite from typical metaluminous granitoid compositions is also light REE-enriched, but peaks at Pr or Nd (somewhat less commonly at Ce and rarely at Sm), having values as high as about 12000 times chondrite. A distinct but less widespread REE pattern observed in some IOCG titanite grains is represented by a marked middle REE enrichment peaking at Sm, Gd or possibly Eu, to about 8000 times chondrite. This latter REE pattern is attributed to a later hydrothermal or metamorphic growth when the light REE are no longer available. In titanite from both magmatic and metasomatic systems, Eu anomalies (Eu/Eu*) may be positive or negative, although within a given sample set, particularly among analyses with overall higher REE concentrations, negative Eu anomalies tend to dominate. In addition to differences in REE abundances and patterns, other trace elements may also be distinctive in metasomatic IOCG titanite, and may indeed provide complementary petrogenetic information. Whereas the generally similar REE patterns appear to be largely a function of fluid chemistry, greater variability in trace transition metals such as Sc, V and Cr demonstrates a more significant dependence on the composition of the rock column through which the mineralizing fluids passed.
Please cite as: Mazdab, F.K., Wooden, J.L. and Barth, A.P. (2007) Trace element variability in titanite from diverse geologic environments. Geological Society of America Abstracts with Programs 39 (6) p.406.
Abstract: Titanite (ideally CaTiO[SiO4]) is a widespread mineral in a variety of igneous, metamorphic and hydrothermal rocks. Among the common accessory phases, titanite is of particular geochemical interest because it can incorporate a diverse suite of trace elements (including U and Th, of geochronologic value, and Zr for geothermometry) that may be diagnostic of the local chemical and P-T conditions of its formation. To explore these compositional variations, we used the Sensitive High-Resolution Ion Microprobe (SHRIMP-RG) to measure the trace element contents of titanite from a reconnaissance collection of differentiated calc-alkaline granitoids, mid-ocean ridge (MOR) mafic intrusives, mixed-protolith eclogite-facies gneisses, and alkali-chloride metasomatic assemblages accompanying Fe-oxide-Cu-Au (IOCG) mineralization. The SHRIMP-RG is ideally suited for these measurements, coupling extreme mass resolution necessary to eliminate most problematic molecular interferences with high sensitivity and fine-scale spatial and depth resolution. Analytical data confirm extreme variability in rare earth element (REE) abundances both among the different rock types and within sets of zoned crystals from individual samples. Chondrite-normalized REE patterns may show peak enrichments in the LREE (La-Nd, with a maximum typically at Pr or Nd), MREE (Sm-Dy) or HREE (Ho-Lu), or can be virtually flat. Concentrations of dominant REE approach 10000 times chondritic values for titanite from many of the granitoid and hydrothermal samples, but among several of the eclogite and MOR samples the least abundant REE may be less than the chondritic values. Eu anomalies (Eu/Eu*) may be negative or positive, but within a suite trend towards more positive values with decreasing total REE and concomitant decreasing temperature (T). Indeed, a detailed set of titanite analyses from two southern California granodiorites show progressive evolution in Eu/Eu* as well as complex systematic changes in the overall REE pattern curvature as functions of T (calculated by Zr-in-titanite geothermometry). Titanite trace element geochemistry promises to be a valuable complement to other petrologic tools in better understanding diverse geologic processes and environments.
Please cite as: Mazdab, F.K., Wooden, J.L. and Barth, A.P. (2007) Integrating trace element abundances and derived temperatures for zircon and titanite to elucidate petrogenesis of a Cretaceous granodiorite, southeastern California. Eos Transactions Supplement, 88(52), abstract V51C-0713.
Abstract: Zircon and titanite are among the more important accessory phases useful for geochronology and geochemistry. With the advent, calibrations, and subsequent refinements of the Ti-in-zircon and Zr-in-titanite geothermometers, two powerful new methods have become available to track and integrate the compositional variations of these minerals during magmatic processes. Using the SHRIMP-RG, we measured REE, U, Th and other trace elements in co-existing zircon and titanite from a Cretaceous granodiorite from Joshua Tree National Park, California. Concurrent measurements of Ti in zircon and Zr in titanite, coupled with independent assessments of αTiO2, αSiO2 and pressure, allowed the estimation of derived crystallization temperatures TTi-in-zircon and TZr-in-titanite in zircon and titanite, respectively. Data indicate that crystallization of zircon and titanite occurred largely simultaneously, from close to 800 °C (the calculated zircon saturation temperature) down to ~700 °C, with continuing zircon crystallization down to ~650 °C. In zircon, concentrations of both Th and U vary somewhat irregularly with TTi-in-zircon, but with cooling the Th/U ratio decreases steadily from 4 to 0.2. In contrast, Th concentrations in titanite decrease sharply with decreasing TZr-in-titanite, while U contents show two separate trends that intersect at the lowest TZr-in-titanite (~700 °C). Above TZr-in-titanite = 750±10 °C, Th/U decreases steadily from 14 to 4 with decreasing TZr-in-titanite, but below this temperature there is an abrupt change in Th/U to nearly constant values of 0.1-0.5. Total REE concentrations decrease in both zircon and titanite with decreasing temperature, but the observed europium anomalies (Eu/Eu*) illustrate complex, dissimilar trends for each mineral. In zircon, interior zones show constant or decreasing Eu/Eu* (at values of Eu/Eu* <1) with decreasing TTi-in-zircon while outer rims show an increase, but still never attaining Eu/Eu* >1. In titanite, hotter zones have Eu/Eu* <1, but Eu anomalies decrease in magnitude and become increasingly positive (to values of Eu/Eu* >1) in cooler zones. In addition, an abrupt change in slope observed in Eu/Eu* vs. TZr-in-titanite occurs with cooling at 750±10 °C, roughly the same temperature at which the zircon interior-to-rim Eu/Eu* transition is also observed. These data suggest a major physiochemical change occurred in the magma around 750 °C which was manifested in multiple chemical parameters in both zircon and titanite. Additional changes in compositional trends in zircon occur below ~700 °C, likely due in part to the absence of competing titanite crystallization. The evaluation of additional chemical data from the other accessory and major minerals will help elucidate the nature of these and other magmatic processes.
Please cite as: Mazdab, F.K. and Wooden, J.L. (2006) Trace element analysis of accessory and rock-forming minerals by ion microprobe (SHRIMP-RG). Eos Transactions Supplement, 87, abstract V33A-0630.
Abstract: The Sensitive High Resolution Ion Microprobe-Reverse Geometry (SHRIMP-RG) is well suited to in-situ analysis of trace elements in a variety of accessory and rock-forming minerals. Work-to-date has centered on zircon, but compositional data for titanite, monazite, xenotime, apatite and clinopyroxene have also been collected as well. Additional techniques for epidote group and garnet group mineral analysis are being evaluated. Overall, the SHRIMP-RG couples the excellent spatial and depth resolution characteristic of conventional SIMS with high transmission and good, flat-topped peak shape even at extreme mass resolution (M/ΔM = 11000-12000 at 10% peak height), unique to the reverse geometry design. In zircon, this permits the effective resolution of 45Sc+ from 90Zr2+ (M/ΔM = 12660) and 93Nb+ from 92Zr1H+ (M/ΔM = 14330). Zircon and the phosphates are among the most straightforward minerals to analyze; mass interferences tend to be simple and resolvable. In contrast, trace element analyses of the complex silicates require more care. In titanite, the Sr and Zr isotopes, Y and Nb can not be fully resolved from the Ca-Ca and, more significantly, Ca-Ti dimers (M/ΔM = up to 470000), although in many cases the effects of these interferences are almost negligible. In clinopyroxene, epidote and garnet, the family of xCayFezSi16O2-3+ species and comparable molecular ions with Mg and Al limit the ability to detect low concentrations of the REE using high mass resolution alone; some energy filtering or peak stripping is necessary. Despite these considerations, a selection of masses ranging from 7Li+, 9Be+ and 11B+ through to 232Th16O+ and 238U16O+, including the REE and key transition metals can be easily measured in less than 20 minutes. Fluorine, chlorine and phosphorus, traditionally measured as negative ions with a Cs+ primary beam, are nonetheless sufficiently abundant as positive ions to be successfully measured even at low ppm levels. Typical beam diameters down to 20 μm allow in many cases multiple analyses within individual zoned crystals, while the limited 1-2 μm crater depth minimizes unintended sampling of subsurface features. Data from these techniques have wide application in mineralogy and petrology. Ti in zircon and Zr in titanite are the bases for novel new geothermometers for igneous and metamorphic rocks, and some of the T-X relationships of REE partitioning between coexisting monazite and xenotime have also been calibrated. The nature and extent of substitution mechanisms such as [(Sc+Y+REE)P]1[ZrSi]-1 (xenotime substitution) in zircon, [CaTh]1[2REE]-1 (brabantite substitution) and [ThSi]1[(REE)P]-1 (huttonite substitution) in monazite and diverse substitution mechanisms in titanite (involving REE, Nb, Na, Al, and Fe) are all related to local P-T-X conditions and thus provide important clues to processes and environment. The starting point for these and other applications is accurate analytical data from well-characterized mineral zones. Although some extra care is necessary to ensure the best quality data from the more complex silicates, the SHRIMP-RG is the ideal instrument to perform these measurements.
Please cite as: Mazdab, F.K. and Wooden, J.L. (2006) Trace element analysis in zircon by ion microprobe (SHRIMP-RG): technique and applications. Geochimica et Cosmochimica Acta 70(18) (S1) p. A405.
Abstract: The Sensitive High Resolution Ion Microprobe-Reverse Geometry (SHRIMP-RG) is ideally suited to the in-situ analysis of trace elements in zircon. The SHRIMP-RG couples the excellent spatial and depth resolution characteristic of conventional SIMS with high transmission and good peak shape even at extreme mass resolution (M/ΔM = ~12000 at 10% peak height), unique to the reverse geometry design. Although other large magnetic sector mass spectrometers can readily resolve the REE peaks from the REE oxides (M/ΔM = ~7000-9000) and 48Ti+ from 96Zr2+ (M/ΔM = 7760), only the SHRIMP-RG is capable of effectively resolving 45Sc+ from 90Zr2+ (M/ΔM = 12660) while still maintaining reproducible, flat-topped peaks. The addition of precise Sc measurement to analytical routines including Y and the REE thus provides a more complete picture of trivalent lanthanoid (Sc+Y+REE) incorporation in zircon than was previously feasible with other microbeam techniques. Preliminary results demonstrate that evidence for diverse lanthanoid substitution mechanisms can be recognized even within individual grains, reflecting fundamental differences in conditions or process during zircon growth. In addition to Sc, Y and the REE, measurements for P, Ca, Ti, Fe, Hf, Th and U are also part of the comprehensive trace element set determined in zircon. Because the instrument set-up for trace elements is essentially the same as that for zircon U-Pb geochronology (only the magnet’s mass range differs), it is possible to perform U-Pb age dating and trace element analyses in sequential analytical sessions without difficulty. Indeed, limited high mass trace elements (Er, Yb and Hf along with Th and U) are already included in the routine U-Pb age-dating analysis set-up and provide a triage to determine which samples may be of greatest interest for a more detailed trace element study. Ongoing studies at the SHRIMP-RG facility on such diverse topics as magma differentiation and evolution, high pressure metamorphism, and metasomatism have already included critical components of trace element analysis in zircon. Ultimately, coupling zircon REE patterns and elemental ratios (e.g. Zr/Hf, Th/U) with geochronology and emerging techniques in petrology such as Ti-in-zircon geothermometry allows the SHRIMP-RG to offer new insights into many igneous and metamorphic processes.